Electrically heated drum-type furnace



y 1, 1945- H. GALLUSSER ELECTRICALLY HEATED DRUM-TYPE FURNACE Filed July30, 1943 lFaienied May 1,1945

ELECTRICALLY HEATED DRUM-TYPE FURNACE Hans Gallusser, Geneva,Switzerland Application July 30. 1943, Serial No. 496,797 In SwitzerlandJune 22, 1942 3 Claims.

Drum-type furnaces are generally employed for performing chemicalreactions between solid and gaseous bodies. In the case of an exothermicreaction, the heat created may be used I for maintaining the temperaturenecessary for the reaction within the furnace, whereas for anendothermic reaction, the heat required for the reaction as such as wella the heat-losses of the furnace must be replaced. I

In known drum-type furnaces it has been tried to generate the necessaryheat by means of electrical resistances mounted within the furnace. Thishowever did not prove successful, because such resistances deterioratetoo quickly. For this reason, this method of heating cannot bepractically applied, especially not for high temperatures of reaction,such as 900-1100 C.

It has also been tried to generate the necessary heat within the furnaceby means of electrical arcs. This method of heating however cannot beemployed for reactions requiring even and exactly constant temperatures,because of the too high temperature of the arc, because of the danger ofsintering, because of uneven heat-distribution and because of theimpossibility of accurately regulating the temperature by means ofelectrical arcs,

The present invention concerns an electrically heated drum-type furnacewhich eliminates the afore-mentioned disadvantages. It is of the knownrotating type and has aslightly inclined longitudinal axis and differsfrom the known drum-type furnace inasmuch as it is provided over atleast one part of its length with electrical transformers. The wiredcore-legs of the latter penetrate the furnace and its secondary consistsof a metallic cylinder, preferably of iron, which forms a part of theinner wall of the furnace.

This arrangement makes it possible, to generate the heat in greatbeating-surfaces, the temperature of which can be accurately regulatedand controlled. Due to the great heating-surface within the furnace, theheat is evenly distributed from the inside towards the outside so thatthere exists a relatively small temperature-difference between theheating element and the heated body. For this reason, dangerousovertemperatures cannot exist, provided that the temperature has beencorrectly regulated in the first place.

The drawing attached show schematically an example of this invention fora three-phase alternating current system. 7

Figures 1 and 2 show a heating element in ionsitudinal and incross-section.

Fig. 3 shows on smaller scale a drum-type furnace with two heatingelements according to Figs. 1 and 2.

The body A of the heating element is cylindrical and consists of anouter envelope i, a layer 2 of heat insulating material and an innermantle 3. The body A is provided with a magnetic core 4 for athree-phase alternating current system, which is'arranged in such a way,that its primary windings '8 are wound upon the core-leg 5 whichpenetrates the cylinder diametrically. Each core-leg 5 is located withina protecting tube 1, open at both ends and subdivided electrically inthe direction of its longitudinal axis, this protecting tube I. beingsurrounded by a layer of heat-insulating material a. Thi layer a islocated between the protecting tube 1 and a closed. metallic mantle 9,preferably of iron, which forms the secondary of the transformer and atthe same time a part of the interior wall of the furnace. Over one endof each core-leg 5 of the magnet core 4 there is provided a ventilatingfan ill for the purpose of cooling the primary windings 6 and thecore-leg 5.

The body A is provided with spur-rings ii around its circumference, bymeans of which it bears against spur-wheels l2 and isthu able to executea. rotating movement.

Fig. 3 shows a drum-type furnace composed of two heating elements A andthe two pre-heaters B and C. These latter consist each of a cylindricalbody with an outer envelope, an inner mantle and a layer ofheat-insulating material arranged between the outer envelope and theinner mantle.

As will be noticed from the drawing, the two pre-heaters have a smallerdiameter than the heating elements.

The body A, B, C of the furnace is slightly inclined towards thehorizontal plane and the transformers of the two heating elements A aredisplaced with respect to each other.

The two open ends of the furnace are arranged rotatably in twostationary bearings I 3, It, the latter being provided with stuffingmeans to prevent leakage of gas during rotation. Each bearing l3, itforms part of a closed hollow body It, viz IS. A gas-intake I1 isconnected to the hollow body I, whereas a gas-exhaust i8 is connected tothe hollow body IS.

A canal or chute 20 communicating with the hopper l9 protrudes into theopen end of the preheater C.

The lower part of the hollow body I! forms a hopper and is connected tothe chute 2| which in turn communicates with the storage-bin 22.

The transformers are fed over slip-rings 28 mounted on body C.

The furnace according to this invention functions as follows:

When energizing the primary windings 6, an induction current is producedin the metal-cylinder 9, heating the latter. Because of- 'it beingelectrically subdivided, no induction-current is induced'in theprotection tube 1. The heat generated is transmitted to the interior ofthe drumtype furnace. By means of regulating the voltage, thetemperature in the interior of the furnace may be adjusted to thedesired value. On the left side the gas is carried to the furnace bymeans of the gas-intake l1. It then flows through the furnace and leavesthe same at the right hand side -by means of the gas-exhaust H3. The ma=teriai to be heated reaches the furnace on the right hand side by meansof the chute 2| and the hopper l9. As a consequence of the heating andof the rotation of the furnace the material.

to be heated will slowly wander through the furnace in the directiontowards the left hand side and leaves the furnace again through thechute 2| to reach the bin 22.

In the pre-heater C the material is pre-heated by means of the hot gasescoming from the heating elements A. The temperature, necessary for thereaction is reached within these heating elements. At its intake side inthe pre-heater B, the gas is also heated by means of the hot materialleaving the heating elements. This same gas is then heated to thetemperature of the re action within the heating elements in order thatthe chemical reaction may take place.

It is to be noted, that the furnace is rendered sufficiently tight atboth ends by means of the material filling the chutes 2B and 2| as topermit the use of light gases, such as hydrogen, without danger ofleak-losses. In the arrangement according to this invention, theheat-losses are at a minimum.

The body of the furnace may naturally also consist of more than twoheating elements A. and the transformers may be designed for singleormultiphase operation.

What I claim is:

1. In an electric furnace. a cylinder through which material to betreated extends axially, means for rotating said cylinder about itsaxis, said cylinder having an inner liner of metal, a tube extendingtransversely through the cylinder, an electromagnetic winding having acore located in said tube and serving as the primary of an inductionheater, the secondary of which is comprised 'by the cylinder liner, andmeans for supplying electricity to the primary windings during rotationof the cylinder.

2. In an electric furnace, a cylinder through which material to hetreated extends axially, means for rotating said cylinder about itsaxis, said cylinder having an inner liner of metal, a plurality of tubesextending transversely through the cylinder, electromagnetic windingshaving cores located in said tubes and serving as the primary of aninduction heater, the secondary of which is comprised icy the cylinderliner, and means for supplying electricity to the primary windingsduring rotation of the cylinder.

3. In an electric furnace, a cylinder through which material to hetreated extends axially, means for rotating said cylinder about itsaxis, said cylinder having an inner liner of metal, a tube extendingtransversely through the cylinder, an electromagnetic winding having acore located in said tube and serving as the primary of an inductionheater, the secondary of which is comprised by the cylinder liner, meansfor supplying electricity to the primary windings during rotation of thecylinder, and a preheating chamber connected gas tightly at an axial endof said 40 cylinder.

